Your ereader is not authorized to open this book

I am having difficulty transferring library ebook from ADE to Kobo Sage.  Purchased books from Kobo open no problem.  The library ebook looks like it is importing when I disconnect my ereader from PC.  It shows the title of the book as it is loading, then it just turns black and I get an error message "This book is protected by ADE management (DRM).  Because you previously deauthorized your ereader ....."  I have tried to reset everything, my ereader, my computer, my library access, everything.  I have made sure accounts are the same.  Still, nothing is working.